During a recent project, I had discussions with some colleagues and friends of mine about the profitability of CPV systems. Many of them did not believe it to be interesting, especially compared to CSP.

I decided then to compare the pros and cons of the three branches of solar power generation systems based on solar tracking :

First, I should make clear for you that each one of those categories actually encompasses different sub-technologies. Solar tracking may be along one or two-axis. In particular, the CSP technologies show a great deal of variety between Fresnel, parabolic trough, parabolas and central receivers (there is plenty of literature available around there). CPV systems are usually not as well known but there is also very different systems : inflatable parabolas (Cool Earth Solar), Fresnel lenses (Concentrix solar), parabolic trough (Exosun), panels of small parabolas (Solfocus) and I am probably missing many other companies.

Notwithstanding these differences, I chose to distinguish only the 3 categories mentioned above.

Flat PV vs CPV

We start with the easiest comparison.

Cons of CPV compared to Flat PV:

you only capture the DNI (direct normal irradiation)

Pros :

Price per peak watt, given that your concentrating systems costs less per unit of surface than the PV cells.

If your do cogeneration of heat using the (absolutely required) residual heat of cooling system, it is much easier to achieve significant temperatures (i.e. 60ºC)

So choosing CPV instead of flat PV can be summarized in two short questions :

“How much radiation do I loose because of diffuse radiation and how much cheaper per unit of surface is my CPV compared to flat PV ?”

“Could I use most of the residual heat ? Does it have an economic value for me ?”

CPV vs CSP

CSP systems are great toys for engineers : they are complex and require a very multidisciplinary knowledge. However, that engineers enjoy working on them is not what will make them successful on the market.

The main advantage of CSP compared to CSP is its capacity to produce also during night time (using thermal storage). Unfortunately, as far as I know, there is no country giving any special incentive for this. Thus, to the investors, it is irrelevant.

The other advantage is that, at the present time, big CSP power plants are able to produce electricity at a cheaper cost than CPV. However, CPV systems are more recent and prices may go down in the future as experience is gained.

Cons of CSP compared to CPV :

Not very scalable (although some organizations are working on the smaller end of the power range)

More maintenance leading to more O&M costs for small plants.

Pros :

Lower costs if you can reach a size big enough.

Capable of operations during night (but as stated earlier, it may not be valued economically).

Possibility to do cogeneration with higher temperatures (above 100ºC). This has not been exploited much so far, but there has been enough research suggesting that industrial applications are possible.

PV generators are quite uninteresting for engineers : it is almost too easy. But that is exactly what makes the beauty of it. The cost PV also already decreased seriously these last years and will cary on. On the other hand, that cost decreases are possible in CSP is not yet a clearly established fact .. but many companies are betting their money on it.